Most notably [KeePassX](https://github.com/keepassx/keepassx) (port of KeePass) is released under the terms of the [GNU General Public License](https://www.gnu.org/licenses/gpl.html).

It doesn't have a direct port to iOS, but the database format is standard across KeePass-family and you can use another client for iOS, like [MiniKeePass](https://github.com/MiniKeePass/MiniKeePass) (also GNU General Public License).